Lecture 6 Medicine Fatty Acids Hydroxy-Keto Acids 2023 PDF

FATTY ACIDS HYDROXY & KETO ACIDS DR. KHATUNA BARBAKADZE Fatty Acids Structural Isomerism There are known more than 200 fatty acids As a rule, they include even number of carbon atoms They differ in...

FATTY ACIDS HYDROXY & KETO ACIDS DR. KHATUNA BARBAKADZE Fatty Acids Structural Isomerism There are known more than 200 fatty acids As a rule, they include even number of carbon atoms They differ in – Branching – Number and position of double bonds – Length of the chain Usually, one deals with fatty acids containing 16-20 carbon atoms Saturated Fatty Acids Melting Points Unsaturated Fatty Acids  Melting Points Unsaturated fatty acids have lower melting points than saturated fatty acids  Nomenclature of unsaturated Fatty Acids digital symbol is 20:4(5,8,11,14) 11-Z 14-Z 8-Z 5,8,11,14-all cis, 20:4 5-Z Arachidonic acid total number of atoms: 20 (eicosa-5(Z)-8(Z)-11(Z)-14(Z)-tetraenoic acid) Nomenclature of unsaturated Fatty Acids HYDROXY & KETO ACIDS Learning Objectives: Classification / Nomenclature / Physical properties Acidity Chirality Tautomerization Reactions  Important class of organic compounds that contain hydroxyl & carboxyl functional groups at the same time Most often, the hydroxyl group is a secondary alcohol group ✓ If the ɑ-Carbon contains 2 different substituents than it presents a stereogenic center. ✓ Therefore, if an ɑ-hydroxy acid is a secondary alcohol, it always contains a potential stereogenic center in the ɑ-position. ✓ As for β-, γ-, δ-, ε-hydroxy acids, we have to ascertain the presence of stereogenic centers by the common rules. ✓ Some of α-hydroxy acids have a side chain that also contains another carboxyl group. ✓ Such hydroxy acids are di- or triprotic acids. ✓ Di- and triprotic hydroxy acids can be ɑ-, β-, γ-, acids at the same time Tartaric acid contains 2 stereogenic centers but two of its 4 possible configurations are symmetric and present the identical meso-compound, therefore tartaric acid has three configurations: (-)-tartaric acid, (+)-tartaric acid and meso-tartaric acid Stereoisomer Configu- Melting Optical Density Solubility at 20°C ration point rotation [α]D (g/ml) (g/100 ml H2O) (°C) (degree) (+)-Tartaric 2R,3R 168 - + 12 1.7598 139.0 acid 170 (-)-Tartaric 2S,3S 168 - - 12 1.7598 139.0 acid 170 meso-Tartaric 2R,3S / 2S, 146 - 0 1.6660 125.0 acid 3R 148 Racemate of 2R,3R und2 206 0 1.7880 20.6 tartaric acid S,3S  The most important representatives of phenolic compounds containing carboxyl groups Acidity Examination of the heating products of hydroxy acids allows to identify the position of the hydroxyl group with respect to the carboxyl group (cyclic diesters) Gem-diols (carbonyl hydrates) of α-keto acids are much more stable than those of unsubstituted ketones: The same reaction carries out similarly for other α-keto acids The same reaction carries out similarly for other α-keto acids Decarboxylation of β-keto acids